Mixing apparatus

ABSTRACT

A mixing apparatus in which a suspension is to be subjected to a dispersing treatment with the help of a particulate dispersing aid. A housing has a chamber in which a rotatable shaft carrying one or more impellers is mounted to thereby agitate a mixture of a suspension with a particulate dispersing aid which has been admitted into the chamber. Outlet means for the treated suspension is provided and comprises an annular member having a center opening which communicates with the exterior of the chamber and a cooperating disc member which overlies the center opening and defines with the annular member an annular radial gap communicating with the center opening and so dimensioned that the treated suspension can pass therethrough but that the particulate dispersing aid is retained. The disc member is so mounted that it can turn or rotate with reference to the annular member but is completely independent of the rotatable shaft or any other drive means, that is it rotates freely.

United States Patent [151 3,679,183 Bachofen [451 July 25, 1972 54] MIXING APPARATUS Primary Examiner-Robert w. Jenkins [72] Inventor: Willy A. Bachofen, Utengasse l5, Basel, Attorney-Michael Smker 57 ABSTRACT [22] Filed: April 14, 1971 A mixing apparatus in which a suspension is to be sub ected to [21] Appl. No.: 133,974 a dispersing treatment with the help of a particulate dispersing aid. A housing has a chamber in which a rotatable shaft carry- 30] Foreign Application Priority Data ing one or more impellers is mounted to thereby agitate a mixture of a suspension with a particulate dispersing aid which has March 1970 Switzerland been admitted into the chamber. Outlet means for the treated suspension is provided and comprises an annular member hav- [52] US. Cl ..259/9 ing a center opening which communicates with the exterior f [51] Int. Cl. B01! 7/04 the chamber ahd a cooperating disc member which own-hes [58] Field of Search ..259/9, 10, 25, 26, 45, 46, the center opening and defines with the annuar member an 259/5 6 annular radial gap communicating with the center opening and so dimensioned that the treated suspension can pass [56] References Cited therethrough but that the particulate dispersing aid is UNITED STATES PATENTS retained The disc member is so mounted that it can turn or rotate with reference to the annular member but is completely El'lCkSOl'l indcpendent of rotatable haft or any other drive means 3,246,594 4/1966 Fisher that is i rotates f 3,288,443 11/1966 Lynch ..259/9 12 Claims, 2 Drawing Figures 5 16 1A 140 13 1a 6 Mb O I 23 17 1. A a i n a I 4i H z I 1 in li i i l 1 1 i 1 i f H fl L i i i l J P -a 1:. i I l' Mali 1 I I l ll l l aw: mm- Lfl l l i L was new sum 2 or 2 Dvepm: M 4, 1-; 4 110. 1/14,

MIXING APPARATUS BACKGROUND OF THE INVENTION The present invention relates generally to the imposition of a mixing action upon liquids, and more particularly to a mixing apparatus. Still more specifically the present invention relates to a mixing apparatus for subjecting suspensions to a dispersing treatment with the help of a particulate dispersing aid.

It is already known that if a suspension is accommodated in a mixing apparatus together with a particulate dispersing aid, that is a quantity of particles which are larger than those in the suspension, then the rotary movement imparted to the mixture in the mixing apparatus will in effect cause the larger particles of the dispersing aid to shear through the suspension, whereby the latter is subjected to a very fine dispersion treatment. Once the requisite degree of dispersion treatment has been achieved, the treated suspension must of course be removed from the mixing apparatus and the larger-dimensioned dispersing aid particles be retained to effect the necessary separation of the two. A device utilizable in this manner is already known. In it the outlet is provided with an annular member which is stationarily mounted and adjacent to which there is mounted a disc member overlying the center opening of the annular member and defining with the latter a radial gap communicating with the center opening and through which the treated suspension flows out of the chamber. The disc member is connected with the shaft carrying the impeller or impellers of the known device, either in a completely fixed relationship -that is capable neither of turning with reference to the shaft nor performing axial movements relative thereto-or at least in non-rotatable manner so that it must rotate with the shaft.

The thus-imposed rotation of the disc member with respect to the stationary annular member is in itself desirable, because it performs a self-cleaning action in the annular gap, thereby avoiding the danger that the gap might become clogged by particles which become lodged in it. Practical application of this prior-art construction has shown, however, that the device is possessed of certain disadvantages. The charge of particles constituting the particulate dispersing aid sometimes contains undersized particles, that is particles which are smaller than the established dimensional range. Even if that is not the case, however, it will be appreciated that the particles are subject to some size reduction due to abrasion resulting from contact with other particles during the mixing process. When such undersized particles enter into the gap, then they are not retained therein but instead are crushed by the relative movement between the disc member and the stationary annular member. It is thus found that in a finely dispersed suspension having been treated in this prior-art apparatus, there will always be traces of crushed dispersing aid particles. This, however, reduces the quality of the treated suspension and, in some circumstances, makes the suspension entirely unusable.

A further disadvantage discovered in conjunction with the prior-art apparatus described above, is the fact that the width of the radial annular gap defined between the stationary annular member and the rotatable disc member cannot be main tained unchanged with sufiicient accuracy during the mixing process. The reason for this is that the rotating component, that is the disc member, is mounted on the vibrating drive shaft which turns the impeller or impellers, and consequently the gap width which is previously set with a micrometer when the device is not in operation, cannot be maintained constant during such operation.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome the aforementioned disadvantages of the prior art.

More particularly it is an object of the present invention to provide an improved mixing apparatus of the type under discussion which is not possessed of these disadvantages.

In pursuance of these objects, and of others which will become apparent hereafter, one feature of the invention resides in a mixing apparatus, particularly for subjecting suspensions to a dispersing treatment with the help of a particulate dispersing aid, which mixing apparatus comprises, briefly stated, housing means defining a chamber and inlet means for a suspension to be treated as well as for particulate dispersing aid. Mixing means is provided in the chamber and includes arotatable shaft and at least one impeller thereon for rotary agitating of the suspension and aid to thereby subject the former to fine dispersion with the help of the latter. Outlet means is provided for the treated suspension and is spaced from the mixing means; this outlet means comprises an annular member having a center opening and a cooperating member overlying the center opening and defining with the annular member an annular radial gap which communicates with the center opening and which is dimensioned for passage of the treated suspension but for retention of the particulate dispersing aid. Finally, there is provided mounting means which mounts at least one of the members for rotational movement with reference to the other member under the influence of the rotating suspension.

The member which is mounted for rotational movement will normally be the cooperating member, and according to the present invention it must be freely tumable but connected neither with the shaft nor with any other drive means in a mechanical manner. It can be completely freely turnable or it can be under the influence of an energy-storing device, such as a spring, which during turning movement of the cooperating member will become tensioned to thereby store energy which is then released when the rotation of the contents of the chamber ceases to thereupon return the cooperating member to its initial position.

It is advantageous to provide the cooperating member, preferably on the side thereof facing towards the shaft of the mixing means, with at least one or several projecting wings exposed to the rotating liquid so that the latter can more readily turn the cooperating member. Also, the axis of rotation of the cooperating member need not be coincident with the center of the annular radial gap.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical longitudinal section through an apparatus according to the present invention; and

FIG. 2 is a fragmentary vertical longitudinal section, on an enlarged scale, through the apparatus of FIG. 1 but showing certain details thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing in detail, it will be seen that in FIG. 1 I have illustrated an apparatus embodying the present invention. The apparatus comprises a support or base 1 carrying the electromotor 2 which is diagrammatically illustrated. In known manner the output shaft of electromotor 2 is provided with a drive pulley 3 which is connected via drive belts 4 with a further drive pulley 5 mounted on one end of a shaft 6. The shaft 6 is turnably journalled in bearings 7 and 8 and provided on its right-hand section 6a-which may be of other-thanround cross-section, such as of quadratic cross-sectionwith several axially spaced transversely extending impellers 10 which are spaced from one another by spacing sleeves 9 surrounding the shaft section 6a intermediate the impellers 10. The construction of the impellers 10 is of no importance for purposes of the present invention, but it must be kept in mind that they must be balanced to avoid the generation of excessive vibrations in the shaft 6 when the same rotates. The shaft 6 with the impellers l constitutes mixing means for the apparatus, and a terminal impeller 12 is secured to the shaft section 6a by means of a screw 13 or the like, which thus holds all of the components-that is the impellers and 12 and the spacing sleeves 9-in place.

The apparatus further comprises a cylindrical housing 14 which is removable and retained in place by means which are not separately illustrated, being of no importance for the present invention. The housing 14 surrounds the shaft section 6a with the impellers 10 and 12 and has an interior chamber as illustrated. It is also provided with a double wall 14a to create a jacket for the circulation of a cooling or heating fluid, and end walls or covers 14b and 14c close the opposite open ends of the housing 14.

An inlet conduit 16 is mounted in the end wall 14b and receives in a non-illustrated manner and from a non-illustrated source the suspension to be treated. An opening 20 is provided through which particulate dispersing aid can be introduced into the interior of the chamber. The other end wall 140 is preferably pivotably mounted on the housing 14 and is retained in closed position by means of screws or bolts 17. It carries the outlet conduit 18a for the treated suspension.

Thus far the apparatus of FIG. 1 is conventional and it will be recalled that the suspension is introduced through the inlet 16 and the particulate dispersing aid through the opening 20. The mixing means turns at high speed and imparts to the mixture of suspension and particulate dispersing aid a rotary movement, causing the particles of the dispersing aid to shear through the suspension and to thereby effect the desired fine dispersion. The treated suspension, that is the suspension which has been treated to obtain the desired fine dispersion, leaves the chamber in the housing 14 through the outlet conduit 18.

According to the present invention, and as best seen in FIG. 2, the outlet means of the chamber, which communicates with the outlet conduit 18, is provided in form of an annular radial gap 11 defined between a stationary annular member 19 mounted on the end wal 14c and a cooperating member 21 which here is also of annular configurationwhich overlies the center opening in the annular member 19 and defines with the latter the annular radial gap 11. The member 21 is retained in position by means of two engaging members 22 and 24 which mount it on the shaft 23, the members 22 and 24 being connected with the shaft 23 by means of a screw or similar element 25. It is to be noted that the shaft 23 is entirely unconnected with the shaft 6. It is further pointed out that the annular member 19 could also be located at the opposite side of the member 21, that is the side facing towards the shaft 6.

Shah 23 is journalled in bearings 26 and 27 for free rotational movement, and in the illustrated embodiment both the terminal impeller 12 and the member 22 are provided with respective projecting wings 12a and 22a. Thus, when the impeller 12 turns with the shaft 6, the motion caused in the surrounding contents of the chamber by the Wings 120 is transmitted particularly well to the wings 22a and thereby causes the member 22 to rotate. Of course this in turn causes the shaft 23 to rotate which is fast with the member 22, and thus effects rotational movement of the member 21 with reference to the stationary annular member 19. On the other hand, if a particle is lodged in the gap 11, the force transmitted to the member 21 will normally not be strong enough to cause the same to overcome the wedging action of the particle and the member 21 will then remain stationary, thereby avoiding crushing of the particle and its passage out of the chamber with the treated suspension.

In conventional manner the apparatus of FIGS. 1 and 2 may be provided with known means which permit an adjustment in such a manner as to vary the axial width of the gap 11 in order to accommodate this width to the dimensions of the particles of the particulate dispersing aid which are being used.

It is clearly not necessary that the axes of rotation of the shafts 6 and 23 be precisely coaxial, although this is the case in the illustrated embodiment. Also, if the juxtaposed major surfaces of the members 21 and 19 which between them define the gap 11 are located in planes which exactly normal to the axis of the shaft 23, then it is not even necessary that the members l9 and 21 themselves be exactly concentric with reference to the axis of rotation of the shaft 23. This would be necessary only if the major surfaces defining between themselves the gap 1 1 should be tapered, or conical.

It will also be appreciated that the wings 12a and 22a could be replaced by magnetic devices in order to thereby obtain in effect a magnetic coupling causing the shaft 23 to rotate with the shaft 6 in the absence of a force acting in the gap 11 which could prevent such rotation, but in any case effecting such rotation of the shaft 23 without direct mechanical coupling with the shaft 6.

According to a further embodiment of the invention it is also possible to connect the shaft 23 via an energy-storing device such as a spring with housing 14 or with the casing 28 mounting the shaft 23 in such a manner that as the member 21 and the shaft 23 are rotated by the rotating contents of the housing 14, the spring will become tensioned; in such embodiment the member 21 and the shaft 23 could of course be rotated only through a predetermined limited extent, for instance a portion of arc, and when the operation of the mixing means is terminated and rotation of the contents of the housing 14 stops, the stored energy would be released from the spring and would turn the shaft 23 in the opposite direction to restore it to its starting position. Thus, whenever the operation of the mixing means would be terminated or interrupted, a self-cleaning of the gap 1 1 would take place.

It is also not necessary for the member 21 to be precisely of circular outline. It may have a different non-circular but rounded outline, for instance an elliptical configuration. The axis of rotation of the member 21 also need not be coincident with its center, as long as the resulting eccentricity is not so substantial that the gap width changes when the member 21 is subjected to rotational movement. The member 21 can also be so arranged that its axis of rotation is not only not coaxial but also not parallel with the axis of rotation of the shaft 6; thus, the axis of rotation of the member 21 could for instance extend more or less normal to the axis of rotation of the shaft 6.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a mixing apparatus, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute the essential characteristics of the generic or specific aspects of this invention and, therefore, such adap tations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A mixing apparatus, particularly for subjecting suspensions to a dispersing treatment with the help of a particulate dispersing aid, comprising housing means defining a chamber; inlet means for a suspension to be treated, and for particulate dispersing aid; mixing means in said chamber and including a rotatable shaft and at least one impeller thereon for rotary agitating of said suspension and aid to thereby subject the former to fine dispersion with the help of the latter; outlet means for the treated suspension, spaced from said mixing means and comprising an annular member having a center opening, and a cooperating member overlying said center opening and defining with said annular member an annular radial gap communicating with said center opening and dimensioned for passage of the treated suspension but retention of the particulate dispersing aid; and mounting means mounting at least one of said members for rotational movement with reference to the other member under the influence of the rotating suspension.

2. A mixing apparatus as defined in claim 1, wherein said one member is said cooperating member.

3. A mixing apparatus as defined in claim 2, said mounting means comprising journaling means journaling said cooperating member for free rotational movement with reference to said annular member.

4. A mixing apparatus as defined in claim 1, said shaft and said one member each having an axis of rotation; and wherein the axis of rotation of said one member is at least substantially coaxial with the axis of rotation of said shaft.

5. A mixing apparatus as defined in claim 2, said cooperating member having one side facing said annular member and an other side facing towards said shaft; and wherein at least one of said sides is provided with a projecting wing exposed to the rotating suspension, whereby said cooperating member has imparted to it said rotational movement.

6. A mixing apparatus as defined in claim 5, wherein said one side is said other side.

7. A mixing apparatus as defined in claim 2, said cooperating member comprising at least one projecting wing exposed to the rotating suspension, whereby said cooperating member has imparted to it said rotational movement.

8. A mixing apparatus as defined in claim 2, wherein said cooperating member is a disc member.

9. A mixing apparatus as defined in claim 8, wherein said disc member is of non-circular rounded outline.

10. A mixing apparatus as defined in claim 8, wherein said disk member has a center, and wherein the axis of rotation of said disk member is offset relative to said center.

11. A mixing apparatus as defined in claim 8, wherein said annular radial gap has a center, and wherein the axis of rotation of said disk member is offset with reference to said center.

12. A mixing apparatus as defined in claim 2; further comprising energy-storing means connected with said cooperating member and tending to store energy in response to rotational movement of said cooperating member under the influence of the rotating suspension and in one direction, and to release the stored energy to said cooperating member in the absence of rotation of said suspension. 

1. A mixing apparatus, particularly for subjecting suspensions to a dispersing treatment with the help of a particulate dispersing aid, comprising housing means defining a chamber; inlet means for a suspension to be treated, and for particulate dispersing aid; mixing means in said chamber and including a rotatable shaft and at least one impeller thereon for rotary agitating of said suspension and aid to thereby subject the former to fine dispersion with the help of the latter; outlet means for the treated suspension, spaced from said mixing means and comprising an annular member having a center opening, and a cooperating member overlying said center opening and defining with said annular member an annular radial gap communicating with said center opening and dimensioned for passage of the treated suspension but retention of the particulate dispersing aid; and mounting means mounting at least one of said members for rotational movement with reference to the other member under the influence of the rotating suspension.
 2. A mixing apparatus as defined in claim 1, wherein said one member is said cooperating member.
 3. A mixing apparatus as defined in claim 2, said mounting means comprising journaling means journaling said cooperating member for free rotational movement with reference to said annular member.
 4. A mixing apparatus as defined in claim 1, said shaft and said one member each having an axis of rotation; and wherein the axis of rotation of said one member is at least substantially coaxial with the axis of rotation of said shaft.
 5. A mixing apparatus as defined in claim 2, said cooperating member having one side facing said annular member and an other side facing towards said shaft; and wherein at least one of said sides is provided with a projecting wing exposed to the rotating suspension, whereby said cooperating member has imparted to it said rotational movement.
 6. A mixing apparatus as defined in claim 5, wherein said one side is said other side.
 7. A mixing apparatus as defined in claim 2, said cooperating member comprising at least one projecting wing exposed to the rotating suspension, whereby said cooperating member has imparted to it said rotational movement.
 8. A mixing apparatus as defined in claim 2, wherein said cooperating member is a disc member.
 9. A mixing apparatus as defined in claim 8, wherein said disc member is of non-circular rounded outline.
 10. A mixing apparatus as defined in claim 8, wherein said disk member has a center, and wherein the axis of rotation of said disk member is offset relative to said center.
 11. A mixing apparatus as defined in claim 8, wherein said annular radial gap has a center, and wherein the axis of rotation of said disk member is offset with reference to said center.
 12. A mixing apparatus as defined in claim 2; further comprising energy-storing means connected with said cooperating member and tending to store energy in response to rotational movement of said cooperating member under the influence of the rotating suspension and in one direction, and to release the stored energy to said cooperating member in the absence of rotation of said suspension. 